An Ecological Comparison of Small Abstract: Our studies in similar scrub habitats Communities in California and Chile1 in California and Chile reveal some interesting differences between these two regions in the structure of their small mammal communities. The Chilean fauna is less diverse, with fewer 2 William E. Glanz and Peter L. Meserve per site, and possibly more extreme density fluc- tuations. Chilean are more strongly associated with areas of high shrub and rock cover, while California species show a greater variety of habitat preferences. Chile has more insectivorous species, and California has more seed-eating specialists. Some of these differ- ences may be related to biogeographic and climatic factors, while others may reflect a longer history of human disturbance in Chile.

Similar climates often seem to favor the evo- FIELD SITES AND METHODS lution of similar organisms, and the Mediterranean -climate regions of the world have provided numer- We have ecological data from a variety of ous examples of such evolutionary convergence. communities in each region, but will restrict our Of the five regions with this climate, California discussion here to results from three vegetational and Chile have been compared very extensively types which we have studied intensively: dry (Mooney 1977), particularly in terms of the mor- coastal scrub, moist coastal scrub, and evergreen phological, physiological, and ecological attri- chaparral. For each of these, the vegetation butes of their dominant organisms. Striking structure and life forms at our sites were closely similarities between these two regions have been matched between continents. found in their vegetation structure and community patterns (Mooney and Dunn 1970; Parsons and The dry coastal scrub localities were studied Moldenke 1975; Parsons 1976), their birds (Cody by Meserve near Irvine, Orange County, California 1973 and 1974), and their lizards (Fuentes 1976). in 1970-71 and at Fray Jorge National Park, Coquimbo Province, Chile in 1973-74. Detailed In a variety of projects during the past decade descriptions were provided by M'Closkey (1972) (Meserve 1972, 1976a, 1976b, 1981a, 1981b; Glanz and Meserve (1972 and 1976a) for the California 1977a and 1977b; Meserve and Glanz 1978), we have site, and by Fulk (1975) and Meserve (1981a) for studied certain communities of small in the Chilean site. Both study areas were at about the Mediterranean zones of California and Chile. 200 m elevation, within 5 km of the coast, and In this paper we will summarize our results by were located on sandy, well-drained soils. comparing our three best-documented sites on each Although mean rainfall at the California site continent. We will outline some aspects of these (about 300 mm) was considerably greater than at communities that suggest convergence in morphology the Chilean site (127 mm), their similar topo- and ecology. Our emphasis, however, will be on graphy, seasonality, and soils apparently pro- the ecological differences that we have found duced remarkably convergent vegetation, with between the two regions, especially those relating approximately 60 percent shrub cover dominated by to community diversity, habitat use, and diet. drought-deciduous species. These dissimilarities suggest some major differ- ences in the functional roles of mammals in these The moist coastal sites studied by Glanz communities, some contrasting responses of these (1977a and 1977b) were at Camp Pendleton Marine to vegetation structure, natural preda- Base, San Diego County, California, and at tors, and human disturbance, and some potentially Zapallar and Los Molles (two sites), Aconcagua important differences in the evolutionary his- Province, Chile. Although the rainfall at these tories of the two regions. We hope that our dis- localities (225 to 350 mm) was comparable to that cussion of these topics will stimulate further of the California dry coastal site, they were on research on these ecosystems and their small slopes more directly facing the ocean and received mammal faunas. more coastal fog. This greater moisture plus the higher clay content of the soils resulted in greater average shrub cover (74 percent), also 1 Presented at the Symposium on Dynamics and dominated by drought-deciduous species, but Management of Mediterranean-type Ecosystems, including more evergreen shrubs than the dry June 22-26, 1981, San Diego, California. coastal sites. All study areas were between 20 and 60 m elevation and within 1 km of the coast. 2 Assistant Professor of Zoology, University of Maine, Orono, Maine 04469; and Assistant Pro- The evergreen chaparral sites sampled by fessor of Biological Sciences, Northern Illinois Glanz (1977a and 1977b) were at Echo Valley, University, DeKalb, Illinois 60115. near Descanso, San Diego County, California, and

Gen. Tech. Rep. PSW-58. Berkeley, CA: Pacific Southwest Forest and Range 220 Experiment Station, Forest Service, U.S. Department of Agriculture; 1982. at Fundo Santa Laura, near Tiltil, Santiago Table 1. Occurrence of each small mammal species Province, Chile. Both were at 900 to 1000 m ele- at the California (above) and Chilean (below) vation, had 550 to 600 mm mean annual rainfall, sites. Sites are dry coastal (DC), moist coastal and were dominated by evergreen sclerophyllous (MC), and evergreen chaparral (EC). Abundance shrubs. Plots trapped at these sites averaged 75 values are: X = present, but uncommon; L = locally percent shrub cover. Many additional aspects of common; C = common or abundant. Species Codes are the evergreen chaparral and moist coastal sites used in figures 1 and 2. were studied during the Mediterranean Scrub Project of the International Biological Program, and are Community Type described in detail in Thrower and Bradbury (1977). Species (and Code) DC MC EC CALIFORNIA Our field techniques were designed to sample most mammal species up to 500 gm body size in each INSECTIVORA community. Populations were live-trapped on large Soricidae (1.4 to 2.2 ha) grids at all sites except the Notiosorex crawfordi X X Chilean moist coastal localities, and snap-trapped RODENTIA on small (usually 0.4 ha) grids at all sites except Sciuridae to California dry coastal area. Population den- Eutamias merriami X sities were determined by mark-recapture tech- Spermophilus beecheyi L L niques, and by correlating snap-trap success with Geomyidae live-trapping results. A variety of physical and Thomomys bottae X X vegetational measurements were used to character- Heteromyidae ize the habitat preferences of each species. Dipodomys agilis (Dpa) C C Meserve (1976b, 1981b) categorized each trap Perognathus californicus (Pgc) X X station according to its shrub, herb, and bare Perognathus fallax (Pgf) X C ground cover values, and then conducted 2 x k association analyses (Simpson, Roe, and Lewontin Perognathus longimembris (Pgl) C 1960) between presence/absence data of each Cricetidae species at trap stations and categories of vege- Microtus californicus (Mcc) X C X tation cover. Glanz measured 30 habitat variables Neotoma fuscipes (Ntf) L C C at each trap station, scored each mammal capture Neotoma lepida (Ntl) X C X for the characteristics of that trap station, and Peromyscus boylii (Pmb) L then compared the habitat measures of stations Peromyscus californicus (Pmc) C C C selected by each mammal species with those of all Peromyscus eremicus (Pme) C C X stations trapped at each site. To assess the Peromyscus maniculatus (Pmm) C C C degree of habitat differentiation among species Reithrodontomys megalotis (Rtm) C X X at each site, Glanz also conducted discriminant Muridae analyses using capture records and programs in Mus musculus X X the SPSS computer library. Total Species 12 13 13 Meserve compared arboreal vs. terrestrial Common Species 7 8 6 habitat utilization at the dry coastal sites CHILE using smoked cards placed on the grant and at 25,

50, 100 and 200 cm above ground in the most common MARSUPIALIA shrub species. Tracks on the cards were identi- Didelphidae fied to species and individual using foot charac- Marmosa elegans (Mae) X C X teristics and toe-clip marks (Meserve 1976b and RODENTIA 1981b). Abrocomidae Abrocoma bennetti (Abb) X C Food habits were assessed by microscopic examination of stomach contents and fecal pellets degus (Ocd) C X C at most sites, and by fecal analysis only at the Octodon lunatus (Ocl) L L California dry coastal site. Meserve (1976a and Spalacopus cyanus L X 1981a) homogenized the sample first, subsampled Cricetidae and boiled the material in Hertwig's solution Akodon longipilis (Akl) C C C (Baumgartner and Martin 1939), and then identi- Akodon olivaceus (Ako) C C X fied cell fragments under a microscope at 100X. Oryzomys longicaudatus (Orl) X X X Glanz (1977) quantified stomach content fractions Phyllotis darwini (Phd) C X X first at 40X, subsampled each fraction, and then followed the above procedure. These variations Muridae in methods may limit the precision of our compar- Rattus rattus (Rra) L isons, but should not alter the general conclu- Total Species 7 8 10 sions we present in this paper. Common Species 4 5 5

FAUNAL COMPOSITION AND DIVERSITY each community are listed in table 1. Several points are obvious from this list. First, both The species of small mammal recorded from faunas are dominated by rodents; the only excep-

221 tions are one shrew, Notiosorex crawfordi, in the two continents (p>.10; U-test). The Chilean California and one mouse opossum, Marmosa elegans site had more extreme variations (coefficient of in Chile. Next, the two faunas are phylogeneti- variation = 48.9 in Chile, 16.8 in California), cally distinct. Among the rodents, only one with Akodon olivaceus declining from high densi- native family (Cricetidae) is shared between the ties (32/ha) early in the study and Octodon degus two regions, although each also contains species reaching 120/ha near the end (Meserve 1981b). of murid rodents introduced by humans from Fulk (1975) live-trapped the Fray Jorge site in Eurasia. The cricetid rodents of the two areas, 1972-73 (prior to Meserve's study), and found moreover, are quite distantly related. Following even higher populations, with A. olivaceus and Hershkovitz (1969), all the Chilean cricetids are Phyllotis darwini densities combined exceeding placed in the tribe Sigmodontini, while the genus 300/ha. Glanz (1977) also found higher average Microtus is in the subfamily Microtinae, and all densities and much greater variability at another California species are in the tribe Peromyscini. Chilean dry coastal site (near Guanaqueros, Similarities between these unrelated groups, then, Coquimbo Province) than at its climatic counter- may be considered evidence for evolutionary con- part in North America. Pefaur and others (1979) vergence; dissimilarities, however, may be due to reported on a outbreak in north-central either phylogenetic or ecological factors. Chile in 1972-73, which was dominated by Oryzomys longicaudatus and P. darwini. These data, then, It is also evident from this list that the indicate that small mammal densities are highly California fauna is much more diverse, including variable in these Mediterranean-type ecosystems, 17 species at these sites in contrast to only 10 but that the fluctuations in Chile may be more species at the Chilean sites. This difference extreme. Some Chilean sites never achieved den- was not unexpected, as Greer (1965) and Baker sities as high as their California counterparts, (1967) have noted that the regional faunas of but we have data from at most two years for each Chile are depauperate in comparison with those of site, and further long-term studies may find that similar areas in North America. They related these populations also occasionally show rodent this low diversity primarily to the geographic outbreaks. isolation of Chile, and to the restricted area of temperate biomes in southern South America. MORPHOLOGICAL COUNTERPARTS If similar ecological opportunities are avail- able in the two Mediterranean climate regions, Several of the Chilean small mammal genera one might expect similar numbers of small mammal strikingly resemble certain California genera in species in analogous communities. This prediction morphological characters. The Chilean leaf-eared is not supported, however, as each Chilean site mouse, Phyllotis darwini, and the rice rat, produced fewer species than its counterpart in Oryzomys longicaudatus, are very similar to the California (table 1). Thus, the Chilean fauna is North American Peromyscus species, all being less diverse even when comparing local communities. small mice with large eyes, large ears, and long tails. All are in the family Cricetidae, however, and also resemble other genera that inhabit other POPULATION DENSITIES habitats, so their morphological similarity may not necessarily indicate convergence. A more Given this pattern of a depauperate Chilean striking example of morphological convergence mammal fauna with fewer species per community, one involves the California woodrats, genus Neotoma, might predict that individual species in Chile and the Chilean hystricognath rodents of the might be replacing several analogous species in genera Abrocoma and Octodon. These large rodents California, and that total densities of all are very distantly related, but are very similar species in comparable communities would be simi- in ear and tail length, body size, and coloration. lar. Such "density compensation" (MacArthur and The most obvious morphological counterparts are others 1972) is difficult to test on these the fossorial rodents of these regions, the gopher Mediterranean-climate communities, as total den- Thomomys bottae in California and the coruro sities at certain sites varied by more than 10X Spalacopus cyanus in Chile. Both have reduced between years. Nevertheless, the evergreen eyes, ears, and tail, elongated claws, and stout chaparral and moist coastal sites appear to incisors and cranial structure, all of which are refute this prediction, as the average densities characteristics found in unrelated groups of per snap-trapping grid were significantly lower burrowing rodents throughout the world. They in Chile for each vegetation type (p<.05 for both therefore exhibit convergence, but in a way that comparisons; Mann-Whitney U-test). The evergreen is not specific to Mediterranean-type ecosystems. chaparral live-trapping densities were also lower in Chile (mean = 5.3/ha) than in California (mean Most other small mammals of the two regions = 9.6/ha), but because of great seasonal varia- are more difficult to match with a morphological bility they were insignificantly different counterpart on the other continent. The shrew (p>.05). Density compensation, however, may be Notiosorex and the mouse opossum Marmosa show occurring at the dry coastal sites, as average virtually no anatomical resemblance, but both total densities were actually higher in Chile have dental adaptations for handling insects and (mean = 58.7/ha) than in California (mean = other prey. The Chilean cricetid mice of 41.4/ha), and insignificantly different between the genus Akodon vaguely resemble North American

222 meadow mice, genus Microtus, both having rela- tively short ears and tails, stocky bodies, long claws, and little dorso-ventral countershading. Microtus, however, is much more extreme in all of these features and has a highly specialized herb- ivorous dentition, while most Akodon species are morphologically generalized mice, showing no major differences from other cricetids. The Cal- ifornia Sciuridae, including the chipmunks (Eutamias) and the ground squirrels (Spermophilus) have no obvious morphological equivalents in Chile. The Chilean hystricognath Octodon degus is diurnal, social, and a rough ecological analog of many North American ground squirrels (Fulk 1976; Glanz 1977b), but is much smaller in size, and more similar to the woodrats in body proportions. Perhaps the most conspicuous absences from the Chilean fauna are counterparts for the North American kangaroo rats and pocket mice, family Heteromyidae. No Chilean rodent has the cheek pouches, large auditory bullae, and adaptations for bipedal locomotion of the California hetero- myids, nor their specializations for seed-eating and water retention (Glanz 1977a; Meserve 1978).

This brief review suggests that although some groups on each continent are morphologically con- vergent, the Chilean fauna has a lower diversity of structural adaptations. The California comm- unities have more species with morphological Figure 1. Comparison of shrub cover values (mean, characteristics that have no counterpart in Chile. 2 standard errors, and 1 standard deviation) of A more rigorous morphological analysis (Glanz capture locations for each species with those of 1977a) confirms these general conclusions. all trap stations at each moist coastal site. Species codes are from Table 1. HABITAT SELECTION P. californicus and a third species, Neotoma Although the data on species diversity and fuscipes were much more common in dense shrublands morphological adaptations suggest some important adjacent to the more open study site, which also differences between the small mammals of Califor- implies preferences for high shrub cover. In nia and Chile, they do not deal directly with the contrast, stations with low shrub cover (<50 per- ecological roles of these animals in their comm- cent) were significantly preferred by two other unities. In the next sections we will discuss species, Dipodomys agilis and Peromyscus manicu- the patterns of resource use by small mammals in latus. At the Chilean dry coastal site, two the two regions, focusing primarily on the util- species, Akodon longipilis and Phyllotis darwini, ization of habitat and food. showed associations with moderate to high cover (51 to 100 percent), but no species preferred Intercontinental comparisons of habitat stations with low shrub cover. selection can be difficult if great differences exist in the available habitat features. In our Shrub cover selection by small mammals at the studies, for example, Chilean sites often had moist coastal sites (Glanz 1977a) is depicted in more herbaceous cover and a higher proportion of figure 1, and it shows a similar intercontinental spiny shrubs than their California counterparts, pattern. At the California site, P. californicus and therefore selective use of these habitat and N. fuscipes chose trap stations with shrub types may have been more likely to evolve in cover significantly higher than the site average, Chile. To simplify our discussion here, we will while two other species, Perognathus fallax and consider only certain features that were compar- P. maniculatus significantly preferred stations able between analogous sites. with low shrub cover. At the corresponding Chilean sites, two species, A. longipilis and Percent shrub cover was virtually identical Octodon lunatus, were trapped at stations with between our analogous sites, but the community shrub cover significantly above the site mean, response to this habitat variable was noticeably while no species significantly chose low-cover different in the two regions. Meserve's (1976b stations. An analysis of shrub cover selection and 1981b) 2 X k association analysis of the dry at the evergreen chaparral sites (Glanz 1977a) coastal sites found that Peromyscus californicus produced similar results. Preferences for high and P. eremicus were associated with trap stations cover stations were significant for certain having high shrub cover (>75 percent) in California. species on both continents, with Peromyscus boylii,

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P. californicus, and N. fuscipes selecting such California. Detailed analyses of habitat overlap habitats in California, and Rattus rattus, A. by Meserve (1981b) and Glanz (1977a) support this longipilis, O. lunatus, and O. degus doing so in generalization. Glanz's discriminant analyses of Chile. Preferences for low-cover stations, how- microhabitat selection, for example, found that 93 ever, were again evident only in California, by percent of all species pairs in California showed D. agilis and P. maniculatus. significant differences in habitats used, while only 68 percent of all Chilean pairs could be sig- Several consistent patterns emerge from these nificantly distinguished by habitat features alone. data. First, species that prefer dense cover are relatively predictable from site to site within FOOD HABITS continents; these usually include some of the larger mice (notably P. californicus in California Assuming that the similar vegetation patterns and A. longipilis in Chile) and the large woodrat and climates of these regions produce similar var- N. fuscipes or its analogs (especially O. lunatus). ieties of potential foods for mammals, one would Most of these high-cover species have ranges expect to find similar dietary patterns in these closely associated with Mediterranean scrub and communities. Our analyses of mammal food habits, associated forest and scrub ecosystems. Next, however, show some remarkable contrasts. Meserve Chile very obviously lacks species that prefer (1976a, 1981a) compiled dietary data throughout low-cover habitats, while California has several. the annual cycle at the dry coastal site, while Finally, at all the California sites the species Glanz (1977a) restricted his analyses to spring that choose open habitats always include one and summer seasons only. Since food habits vary heteromyid (Dipodomys or Perognathus species) and considerably over the seasons, we will restrict one small cricetid, P. maniculatus. Heteromyids our comparisons here to just spring and summer are dominant members of desert rodent communities results. Figure 2 summarizes the diets of most in North America, while P. maniculatus is very species at the three site types. Spring and summer widespread on the continent and frequently results have been averaged, and the food types occupies arid and marginal habitats. have been combined into three general categories: vegetative parts of plants, seeds and fruits, and animal material. In this figure, each apex repre- Rocky habitats also provide important cover to many species. The dry coastal sites had very sents a diet composed entirely of that food type. The further a species is from an apex, the lower few rocky stations and this variable was not the proportion of that food type in the diet. studied there. At the moist coastal sites, three Chilean species (O. lunatus, P. darwini, and A. Several points are immediately apparent from longipilis) were usually trapped near rocks, but these diagrams. First, most communities had one these preferences were not significant, possibly because of few rocky trap stations. More rocky to three leaf-eating species, and these always included the larger genera Abrocoma, Octodon, and habitats were sampled at the evergreen chaparral Neotoma. The diets of these "woodrat" analogs, sites, and the two communities showed contrasting trends. While both localities had species with thus, seem to have converged on leaves, particu- larly shrub foliage, as the principal food. The significant preferences for rocky cover (P. boylii, Octodon species, however, ate more herb leaves, P. eremicus, and Perognathus californicus in Cal- ifornia, O. lunatus and M. elegans in Chile, Cal- and in some seasons seeds and fruits comprised up to 45 percent of their diet (Glanz 1977a; Meserve ifornia had two that significantly avoided rocky 1981a). stations (D. agilis and P. maniculatus) and Chile had none. Other evidence from the small snap-trap Most communities also included species that plots suggests Chilean mammals favor rocky areas. fed largely on seeds, but California sites usually Average density on these grids in Chile tended to increase with percent rock cover (r=.51; .05

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environmental vs. phylogenetic factors on such evolution. We would now like to present several major questions raised by our data and speculate on some alternative answers to these questions.

First, why are small mammals in Chile so insectivorous? Conceivably other animals could be assuming this trophic role in California. Shrews, for example, are the dominant insectivorous mammals elsewhere in North America, and we certainly did not sample adequately our one species, Notiosorex crawfordi. Considering how infrequently we trapped, sighted or found evidence of this species, however, we doubt that it is as common as Marmosa and Akodon species are at corresponding sites in Chile, but we urge further study of this interes- ting shrew. Insects may be more abundant and more predictable in Chile, and therefore may offer more opportunities for dietary specialization by mammals. Comparative data on flying insects of the two regions (Mooney 1977, p. 174) seem to support this idea, but more data on ground-dwelling species would be helpful. Alternatively, Chilean small mammals may represent lineages that tend toward insectivory irrespective of available resources. Elsewhere in South America, most small marsupials and many akodont rodents are also insectivorous (Hershkovitz 1969; Glanz 1977a; Pizzimenti and DeSalle 1980), but the diets of relatively few species have been studied. Morton (1979), in his comparison of North American and Australian desert mammals, found a strong bias toward insectivory in the marsupial-dominated Australian fauna.

Why is the Chilean fauna less diverse? We have mentioned above the hypotheses of Baker (1978) relating faunal size to geographic isolation and the relatively small area of temperate South Amer- Figure 2. Food habits of small mammals at each ica. The mammal fauna of Chile's scrub zone, then, site expressed as proportions of diets for each may be a subsample drawn from a more depauperate food type. See text for detailed discussion. zoogeographic source than for the California fauna. Species codes are from Table 1. Clearly, more studies of their phylogenetic rela- tionships to other temperate and tropical faunas A final point is even more obvious from Figure will be necessary to properly test this idea. 2. California had no primarily insectivorous Equally important will be studies of faunal isola- species, while Chile had two. The mouse opossum, tion through time. The Chilean Mediterranean zone M. elegans, was almost entirely insectivorous, is currently separated from other scrub habitats while A. longipilis fed seasonally from 33 to 73 by the Atacama desert, the Andes, and the Valdivian percent on invertebrates. A. olivaceus showed forests, but it is unclear how important these similar, but more omnivorous feeding trends, with barriers have been in limiting dispersal by diff- insects comprising from 13 to 55 percent of its erent mammal groups. Speciation patterns within seasonal diets. In addition to invertebrates, Chile may also have limited mammal diversity small lizards were occasionally found in the diets (Fuentes and Jaksić 1979) and certainly require of both M. elegans and A. olivaceus. These Chilean more study. species, then, are trophically distinct from the small mammals studied in California. Finally, why have no Chilean mammals evolved into a heteromyid analog, specializing on seeds and open habitats? First, Mares (1976) has found that DISCUSSION no South American rodents are as morphologically specialized for open habitat as the heteromyids, The preceding data outline some possible and that historical factors provide plausible examples of ecological convergence, but emphasize explanations for this contrast. Nevertheless, some some interesting cases of "nonconvergence" in the rodents of other South American scrub areas, such organization of these mammal communities. These as Eligmodontia typus of Argentine deserts, show patterns raise numerous questions regarding the more arid adaptations than any Chilean rodent, so evolutionary pathways followed by the different additional factors may have influenced the Chilean mammal lineages, and-the relative importance of fauna. Perhaps the extreme fluctuations of rainfall

225 in the semi-arid zones of Chile (Fulk 1975; Mooney Norman J.W.; Bradbury, David E., eds. Chile- 1977) produce less dependable food supplies in California Mediterranean scrub atlas: a compar- open habitats than in California. More likely, the ative analysis. Stroudsburg, Penna.: Dowden, availability of these open areas may have been Hutchinson & Ross; 1976b:232-237. different through evolutionary history. The Cal- Greer, John K. Mammals of Malleco Province, Chile. ifornia flora has many fire-adapted species (Mooney Publ. Museum, Michigan St. Univ., Biol. Series 1977), and fires have probably been frequent in the 3:49-152; 1965. past, creating open habitats with which many rodents Hershkovitz, Philip. The Recent mammals of the have coevolved (Quinn 1980). In contrast, the Neotropical region: a zoogeographic and ecolog- Chilean flora has few fire adaptations, fire has ical review. Quarterly Rev. Biol. 44:1-70; 1969. probably been less important there, and no rodents MacArthur, Robert H.; Diamond, Jared M.; Karr, have coevolved with such disturbance. Most open James R. Density compensation in island faunas. habitats in the present scrub zones of Chile may Ecology 53:330-342; 1972. be associated with recent land use practices by Mares, Michael A. Convergent evolution of desert humans (see Bahre 1979; Mooney 1977), and the local rodents: multivariate analysis and zoogeographic mammals have not specialized on these disturbances. implications. Paleobiology 2:39-63; 1976. Finally our data show that certain opportunistic M'Closkey, Robert T. Temporal changes in popula- species (especially P. darwini and A. olivaeus) do tions and species diversity in a California rodent use these open habitats, but primarily at peak den- community. J. Mammalogy 53:657-676; 1972. sities, when other habitats are also occupied. Meserve, Peter L. Resource and habitat utilization They thus may be analogs of the similarly opportu- by rodents of the coastal sage scrub community. nistic and eruptive P. maniculatus, which occupies Ph.D. dissertation. Univ. California, Irvine; low-cover habitats in California. Additional eco- 1972. 248 p. logical and behavioral comparisons of these species Meserve, Peter L. Food relationships of a rodent might prove very interesting. fauna in a California coastal sage scrub commu- nity. J. Mammalogy 57:300-319; 1976a. The small mammal faunas of California and Meserve, Peter L. Habitat and resource utilization Chile, thus, show some striking differences in by rodents of a California coastal sage scrub certain ecological features. We hope that our community. J. Animal Ecology 45:647-666; 1976b. discussion of these examples of "nonconvergence" Meserve, Peter L. Trophic relationships among small will stimulate further research on these animals. mammals in a Chilean semiarid thorn scrub commu- nity. J. Mammalogy; 1981a, in press. ACKNOWLEDGMENTS Meserve, Peter L. Resource partitioning in a Chilean semiarid small mammal community. J. Animal Ecol- Dissertation work by Glanz was supported by NSF ogy; 1981b, in press. grant GB-31195 to Robert K. Colwell; by the Univer- Meserve, Peter L.; Glanz, William E. Geographical sity of California, Berkeley; and by the IBP Medi- ecology of small mammals in the northern Chilean terranean Scrub Project. Meserve's thesis work was arid zone. J. Biogeography 5:135-148; 1978. supported by the University of California, Irvine, Mooney, Harold A., ed. Convergent evolution in and an NIH traineeship. In Chile Meserve was an Chile and California. Stroudsburg, Penna.: assistant professor in the Laboratorio de Ecología, Dowden, Hutchinson & Ross; 1977. 224 p. Universidad Católica de Chile, Santiago. We thank Mooney, Harold A.; Dunn, E. Lloyd. Convergent evo- Eddie Albright for preparing the manuscript and lution of mediterranean-climate evergreen sclero- Clarence Barber for drawing the figures. phyll shrubs. Evolution 24:292-303; 1970. Morton, S.R. Diversity of desert-dwelling mammals: LITERATURE CITED a comparison of Australia and North America. J. Mammalogy 60:253-264; 1979. Bahre, Conrad J. Destruction of the natural vege- Parsons, David J. Vegetation structure in the Med- tation of north-central Chile. Univ. California iterranean scrub communities of California and Publ. Geography 23:1-117; 1979. Chile. J. Ecology 64:435-447; 1976. Baker, Rollin H. Distribution of Recent mammals Pefaur, Jaime E.; Yañez, Jose L.; Jaksić, Fabian M. along the Pacific coastal lowlands of the Western Biological and environmental aspects of a mouse Hemisphere. Systematic Zoology 16:28-37; 1967. outbreak in the semi-arid region of Chile. Cody, Martin L. Competition and the structure of Mammalia 43:313-322; 1979. bird communities. Princeton, N.J.: Princeton Pizzimenti, John J.; DeSalle, Rob. Dietary and mor- Univ. Press; 1974. phometric variation in some Peruvian rodent comm- Fuentes, Eduardo R. Ecological convergence of unities: the effect of feeding strategy on evolu- lizard communities in Chile and California. tion. Biol. J. Linnean Soc. 13:263,-285; 1980. Ecology 57:3-17; 1976. Quinn, Ronald D. Evolution of habitat selection in Fulk, George W. Population ecology of rodents in Heteromyid rodents in California chaparral. Bull. the semiarid shrublands of Chile. Occasional Ecol. Soc. America 61(2):110 (abstract); 1980. Papers, Museum, Texas Tech Univ. 33:1-40; 1975. Simpson, George G; Roe, A.; Lewontin, R.C. Quanti- Glanz, William E. Comparative ecology of small tative zoology. New York: Harcourt, Brace & mammal communities in California and Chile. Ph.D. World; 1960. dissertation. Univ. California, Berkeley; 1977a; 300 p. Glanz, William E. Small mammals. In: Thrower,

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